Dissociation and Lactase Activity in Slow Lactose-Fermenting Bacteria of Intestinal Origin

In 1918 Bronfenbrenner and Davis observed that intestinal bacteria were frequently encountered which failed to show up as lactose fermenters in the routine diagnostic procedure, but which readily did so on subsequent cultivation in media containing lactose in higher concentrations. Studies of the conditions under which the fermentation of lactose by these organisms could be enhanced, with the purpose in view of improving methods for their detection, were reported at that time. Bacteria exhibiting similar variability in fermentation were early described by Neisser (1906) and Massini (1907), under the name Bacillus coli-mutabile. They have been studied more